Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Patent
1991-05-31
1993-03-02
Drodge, Joseph W.
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
55 18, 55 97, 55350, 210 86, 210 87, 210 93, 210 94, 210143, 210335, 210455, 210498, 210745, 210791, 422 55, 422 67, 422101, 422106, 435311, 436177, 436809, B01D 4644, B01D 1712
Patent
active
051906660
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to apparatus for filtering in parallel, i.e. simultaneously and independently, a plurality of samples of fluid (liquid or gas) containing particles to be filtered such as bacteria, cells, or other items, in particular as contained in milk or in blood, the apparatus being designed to co-operate with apparatus for observing and counting the filtered particles. The apparatus of the invention includes a device for automatically monitoring filtered levels and for giving warnings of clogging risks.
At present, small particles present in a fluid in quantities that are small and/or unpredictable are analyzed after being filtered on calibrated filters (of the type known under trademarks "NUCLEOPORE", "MILLIPORE", etc. . . . ). These filters are made by very sophisticated means and are expensive, requiring precautions in use because of their fineness (sometimes less than 10 .mu.m) and because of their fragility.
Examples that may be mentioned include analyses performed in the food industry (milk, beer, mineral water, fruit juice, meat, etc. . . . ) in which the inevitable presence of bacteria must be monitored. With milk, the standard method is the method of culturing in a Petri dish which requires 24 hours to 48 hours to produce a result. Other, quicker methods exist which are usually based on prior staining by means of a fluorochrome, such as Acridine orange. Apparatuses can be put into two categories depending on whether or not the analysis is conservative. Non-conservative apparatuses (continuously) measure stained bacteria using flux (flow cytometer) or distribution techniques on disks or drums.
A priori, these methods are simple, however they do not make it possible to keep a sample for verification purposes, and this is essential in human cytology. They are also unsuitable for properly measuring samples in which bacteria are at a very low density (refined pharmaceutical or food products) and above all products containing artifacts or material in a wide variety of aggregation forms (isolated bacteria or colonies of several thousand bacteria).
Conversely, analyzing filtered samples makes it possible to detect bacteria that are present at very low density and to accommodate the diversity of particles present. However, filters are expensive, operations are lengthy and difficult, and analyzing a sample under a microscope is arduous and slow.
Computer image analysis provides the beginning of a solution to this question by automating sample displacement (using stages with X-Y motor drive in conjunction with a device for automatic Z focusing) and by automatically counting the particles.
With milk, bacteria are present in very variable quantities, and this contributes to setting the price at which milk is bought from a producer.
This density lies in the range 5,000 bacteria per milliliter to 5,000.times.10.sup.4 bacteria per milliliter.
Assuming that the quantity filtered from one sample to another is identical, the quantity of bacteria that may be present in an observation field may vary between 1,000 for contaminated milk to 1 bacterium for every ten observation fileds for milk of excellent quality. It can thus be seen why it is advantageous to modulate the quantity of milk to be filtered, even though a priori this is not possible since it is only the analysis that provides the necessary parameter.
An object of the present invention is thus to provide filter apparatus based on presently known filter techniques while making it possible to obtain sample analyses at a rate that satisfies practical requirements.
The present invention provides filter apparatus for filtering a plurality of samples of fluid (liquid or gas) containing particles to be filtered such as bacteria, cells, or other items, in particular as contained in milk or blood, the apparatus comprising at least one filter and being characterized in that the filter co-operates with means enabling parallel, i.e. simultaneous and independent, filtering to be performed of said fluid samples on the same filter.
In addition, the appar
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Biocom S.A.
Drodge Joseph W.
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